Clinician's Guides to conductive hearing loss in infants and toddlers

Identify CHL in infants

Identifying CHL in young infants can be difficult to do with tympanometry, and there is no standard interpretation. Prieve et al. (2013) evaluated tympanometry variations along with wideband reflectance, and showed the latter was just as effective as tympanometry in identifying CHL in infants.

Prieve et al. evaluated infants less than 6 months old (3-26 weeks) who had been referred in an infant hearing screening program. The babies received both air and bone ABR tests along with tympanometry and wideband reflectance. 43 ears had normal hearing, 17 ears had CHL. Because the number of ears with CHL is small, the diagnostic indicators from this study should be interpreted and used cautiously.

Prieve et al. found that wideband reflectance between 800 and 3000 Hz was higher in CHL ears compared with normal ears. This is consistent with increased stiffness in the middle ear. Prieve et al. found that a criterion for reflectance greater than 69% in the one-third octave band around 1600 Hz produced the highest likelihood ratio for CHL.

Tone or chirp stimuli?

Prieve et al. used the wideband chirp in their study, because they wanted to evaluate multiple frequency ranges. The OtoStat uses a chirp stimulus. HearID can use either a tone or a chirp stimulus: either use the default chirp, or change the stimulus protocol to use a 1.6 kHz tone. The benefit to doing this, especially if you test primarily infants, is that the tone test is faster and achieves a higher signal-to-noise ratio. However, you lose potentially interesting information at other frequencies. Although Prieve et al. didn't evaluate tone stimuli, elsewhere they have been shown to produce identical results (e.g., Hunter et al., 2010).

Interpretation

Fig 3 from Prieve showing 5-95% percentiles for normal and CHL ears. — The blue region shows 5-95th percentile range for reflectance for ears with CHL, and the gray region shows the 5-95th percentile range for normal ears. Around 1600 Hz there is minimal overlap between the two groups. Fig 3 (modified) from Prieve et al., (2013).

Use the Reflectance Area Index (RAI) for the 1/3rd octave around 1.6 kHz for the chirp stimulus, or the reflectance at 1.6 kHz for the tonal stimulus. The RAI is the average reflectance across a frequency region.

An RAI ≥ 69% is consistent with CHL in infants.
An RAI < 69% is consistent with a nomal middle ear (but it doesn't exclude SNHL).

How to run this test

OtoStat 2.0

Choose the Infant age-group.
Make a MEPA measurement and save it. You can optionally continue with the DPOAE measurement, or stop the test early.
Tap on the screen to advance to the analysis screen, or download to review or print the test in OtoStation. The RAI (1.25kHz) is displayed. On the print summary, Prieve's criterion for CHL (above) is also included for comparison.

OtoStat R1

Choose the Infant age-group.
Make a MEPA measurement and save it. You can optionally continue with the DPOAE measurement, or stop the test early.
Review the test on your support computer. On the print summary, the RAI (1.6kHz) is printed out along with the Prieve's criterion for CHL.

HearID v3.x and v5.x

This research was published after HearID's release, so the calculation isn't included in these versions. To make this calculation manually:

For MEPA, either use the default chirp stimulus, or set up the 1.6 kHz tone stimulus manually by following the instructions in the manual. Use the settings: sound pressure level (dB SPL)=60, measurement time (s)=1, and target freqs=1600.
Export the data (see manual) and open in Excel. Find the column "energyReflectance" and take the average between 1414 and 1782 Hz.